Field of the Invention
The present disclosure relates generally to railway vehicle brake equipment. More particularly, the present disclosure relates to an apparatus and method for converting an ABDW control valve to an ABDX-R control valve for use in railway vehicle brake equipment.
Description of the Related Art
Railway vehicle braking systems generally operate by charging and discharging compressed air to and from one or more storage reservoirs located on each railway car. Each storage reservoir is connected to a compressed air source, such as a locomotive air compressor, by a brake pipe. The storage reservoirs are typically separated from the brake pipe by a brake valve which is sensitive to changes in air pressure in the brake pipe. The brake valve senses a pressure drop in the brake pipe and utilizes the compressed air from one or more storage reservoirs to apply the brakes. Because brakes are applied by discharging the air pressure from the storage reservoirs, modern railway vehicle braking systems have a built-in safety feature. In case of a significant air loss, such as during unwanted separation of railway vehicles or a sudden failure of the compressed air source, the brake valve will initiate a full-force, emergency brake application by discharging the compressed air stored in the storage reservoirs.
Railway vehicle braking systems are typically controlled by an operator using a control stand in the locomotive. As the brake valve is moved to release the compressed air in the brake pipe, the loss in air pressure is sensed by individual brake valves on each railway vehicle. Using the air pressure from the one or more storage reservoirs on the railway vehicle, the brake valve applies force on a brake piston to apply the brakes on the railway vehicle. In order to release the brakes, the air pressure in the brake pipe must be restored to cause the brake valve to exhaust the pressure in the brake piston and thereby release the brakes. The system then recharges the air in the storage reservoirs and maintains the air pressure in the brake pipe until the subsequent brake application.
Over the years, a number of railway vehicle braking systems have evolved, the AB-based braking system being the most common. In the AB-based braking system, slight brake pipe pressure reductions do not cause unintended service or emergency brake applications and there is less sensitivity to brake pipe leakage compared to previous braking systems. AB-based control valves receive air from the brake pipe through a cross-over pipe and direct the air to various reservoirs on the railway vehicle during the recharging of the braking system. A plurality of different AB-based control valves have been developed throughout the years.
In one embodiment, an ABD-type control valve includes a pipe bracket and two primary operating portions. Pipe connections from the brake pipe are made to the valve body, which is secured to the frame of a railway vehicle. The two primary operating portions include an emergency portion and a service operating portion. ABD-type control valves include an accelerated release function, where a rapid rise in brake pipe pressure on a first railway vehicle causes a chain reaction on the rest of the vehicles throughout the train and a much quicker release of the brakes.
An improvement to the ABD-type control valve was introduced in 1974 in the form of an ABDW control valve. Its main advancements over ABD-type control valves are a faster brake application and continuous action though an accelerated application valve. The ABDW control valve exhausts air from the brake pipe locally at each car using the accelerated application valve as long as air is being exhausted at the automatic brake valve in the control stand of the locomotive. This causes an accelerated buildup of brake cylinder pressure during service brake applications. During a brake release, the ABDW valve functions in a similar manner to an ABD valve. These control valves are approved for railway vehicles of up to 75 feet in length. Railway vehicles equipped with an ABDW control valve that exceed the 75-foot length must be equipped with additional or supplemental devices to provide an increase in accelerated application valve activity.
The latest improvement to AB-type control valves occurred in 1994 with the introduction of an ABDX control valve. The ABDX control valves are designed for operation on conventional trains and modern freight trains that are longer, heavier, and operate at higher speeds. Whereas ABDW control valves rely on an external accelerated application valve to effect a local exhaustion of air from the brake pipe, ABDX valves have a built-in capability that eliminates the need for an external accelerated application valve. The ABDX control valves provide an improved, more efficient accelerated application valve function, as well as increased stability against undesired emergency applications resulting from fluctuations in brake pipe pressure.
Considering that a plurality of AB-type control valves have been developed throughout the years, railway vehicles traveling on today's railways may be equipped with any of the above-described control valves. While most new railway vehicles are built with the most modern ABDX-type control valves, many existing railway vehicles utilize older, less-effective AB-type control valves, such as an ABDW-type valve. In order to update the braking system of an older railway car to the newest control valve, it is necessary to completely replace an existing ABDW control valve with a new ABDX control valve. The upgrade from an ABDW-type control valve to an ABDX-type control valve provides an improved accelerated application valve and the stability functionality of the ABDX-type control valve.